#canvas{
    background: red;
    display: block;
  }
  body{
    margin: 0;
  }
  .actions{
    position: fixed;
    bottom: 0;
    left: 0;
  }
  .actions > #brush{
    display: none;
  }
  .actions.x > #brush{
    display: inline-block;
  }
  .actions.x > #eraser{
    display: none;
  }